Is there a Linq method to add a single item to an IEnumerable?

Question

Basically I am trying to do something like this:

image.Layers

which returns an IEnumerable for all layers except the Parent layer,

Answer 1

I use the following extension methods to avoid creating a useless Array:

public static IEnumerable ConcatSingle(this IEnumerable enumerable, T value) {
   return enumerable.Concat(value.Yield());
}

public static IEnumerable Yield(this T item) {
    yield return item;
}